[torsen] RE: Torsen differential

Keith Maddock Keith.Maddock at trw.com
Tue Nov 19 04:40:04 EST 2002


Scott/Dave:

Im curious to know how Haldex explained being able to be as proactive as you claim they can be.  Looking at the data on their website, with their electric pump, it seems all they can generate without slip is 4-bar, which is somewhat short of the 30-bar it seems they need for steady-state even torque transfer on a ice launch
http://www.haldex-traction.com/enlarge/graph_ice.htm

Does this "hack" mean overdriving the electric pump for more than 4-bar?  Or does it mean more intelligent control of the releif valves to somehow isolate pressure from the previous slip event in the system.

Also, at 100% lockup, the torque bias is infinite (assuming a strong enough clutch) and will allow 100% of torque to go to front or rear depending on traction conditions at each end.

Also seems we have three definitions of "hang on".  It's been my understanding that "hang on" only describes the mounting configuration of the Haldex brand unit, as it "hangs on" the rear diff.  I wouldn't call the NVG/Jeep unit a "hang on" as it resides in the center transfer case.  I would call the Dana unit on the Escape (same functionality as the Jeep/NVG unit, no electronics) a "hang on".

Cheers,
Keith


****************************************************************
Keith Maddock, TRW Automotive,  Koblenz, Germany
Slip Control Systems, Systems Design, Traction Control
+49 (0)261/ 895 2474     -    -    keith.maddock at trw.com

>>> <QSHIPQ at aol.com> 02:00:20 19.11.2002 >>>
Dave:
This statement is not correct wrt the audi haldex type, this is only true of 
a passive (mechanical) haldex type coupling.  Since lockup is electronic, it 
doesn't at all need slip to be locked.  In fact, audi (or a good hacker) 
could lock it based on factors completely unrelated to slip at all.  This 
would include the electronic NVG models you refrerence in your site.

A haldex LSC as installed in the audi TT should be considered as an "active" 
lockup rear axle, and as such can be controlled or biased in it's current 
design at any point (any time) from 5% rear to 50 rear torque (100%lockup).  
"Hang-on" really describes the lack of center diff, not the actions of the 
coupling.

As such, the haldex TT can be a "full time awd" system, OR a synchro system.  
The unit itself is designed to be either in the TT, audi electronically chose 
it to be synchro (part time 4wd) that's all.  In fact, the engineers at 
Haldex actually indicated that a good hacker could change that retroactively 
without undue stress on the unit as designed.

HTH

Scott Justusson




In a message dated 11/18/02 6:28:27 PM Central Standard Time, 
deaton at tranzrail.co.nz writes:


thanks for all the explanation keith.  i am quite familiar with the haldex,
and the way that it operates.  it is, by definition, a "hang-on" clutch.  it
can be nothing else as the pressure needed to operate the clutch is
generated by slip in the 1st place.  this is the same whether the
application is jeep or audi.  





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